Re: help on packet format for tcp/ip programming
On Feb 8, 3:40 am, Grant Edwards [EMAIL PROTECTED] wrote:
On 2007-02-08, [EMAIL PROTECTED] [EMAIL PROTECTED] wrote:
struct module pack and unpack will only work for fixed size buffer :
pack('1024sIL', buffer, count. offset) but the buffer size can vary
from one packet to the next :-(
Oh for Pete's sake...
struct.pack('%dsIL' % len(buffer), buffer, count, offset)
--
Grant Edwards grante Yow! I want the presidency
at so bad I can already taste
visi.comthe hors d'oeuvres.
that is great but how does one unpack on the other side?
-ishwar
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Re: help on packet format for tcp/ip programming
[EMAIL PROTECTED] wrote:
On Feb 8, 3:40 am, Grant Edwards [EMAIL PROTECTED] wrote:
On 2007-02-08, [EMAIL PROTECTED] [EMAIL PROTECTED] wrote:
struct module pack and unpack will only work for fixed size buffer :
pack('1024sIL', buffer, count. offset) but the buffer size can vary
from one packet to the next :-(
Oh for Pete's sake...
struct.pack('%dsIL' % len(buffer), buffer, count, offset)
--
Grant Edwards grante Yow! I want the
presidency
at so bad I can already
taste
visi.comthe hors d'oeuvres.
that is great but how does one unpack on the other side?
By peeking into the header, determining the number of bytes necessary?
But why do you need this anyway - if you know that you will have python on
both ends, use Pyro or xmlrpc.
Diez
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Re: help on packet format for tcp/ip programming
On Thu, 08 Feb 2007 15:56:30 +0100, Diez B. Roggisch [EMAIL PROTECTED]
wrote:
[EMAIL PROTECTED] wrote:
On Feb 8, 3:40 am, Grant Edwards [EMAIL PROTECTED] wrote:
On 2007-02-08, [EMAIL PROTECTED] [EMAIL PROTECTED] wrote:
struct module pack and unpack will only work for fixed size buffer :
pack('1024sIL', buffer, count. offset) but the buffer size can vary
from one packet to the next :-(
Oh for Pete's sake...
struct.pack('%dsIL' % len(buffer), buffer, count, offset)
--
Grant Edwards grante Yow! I want the
presidency
at so bad I can already
taste
visi.comthe hors d'oeuvres.
that is great but how does one unpack on the other side?
By peeking into the header, determining the number of bytes necessary?
But why do you need this anyway - if you know that you will have python on
both ends, use Pyro or xmlrpc.
Grant had the right idea, I think, but he failed to actually include a
byte length in his format. :) So there's nothing to peek at. If the
packing is done like this, instead..
struct.pack('!IIL', len(buffer), count, offset) + buffer
Then it is a simple matter to unpack it once the receiving side, by waiting
for struct.calcsize('!IIL') bytes, using struct to get len(buffer), count,
and offset:
length, count, offset = struct.unpack('!IIL', bytes)
And then waiting for `length' more bytes, which will be the buffer.
I'm not sure what the original use-case was here. XML-RPC isn't a good
transport for arbitrary binary data. If `buffer' contains text, though,
that might be a good suggestion.
Jean-Paul
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Re: help on packet format for tcp/ip programming
Grant had the right idea, I think, but he failed to actually include a
byte length in his format. :) So there's nothing to peek at. If the
packing is done like this, instead..
struct.pack('!IIL', len(buffer), count, offset) + buffer
Then it is a simple matter to unpack it once the receiving side, by
waiting for struct.calcsize('!IIL') bytes, using struct to get
len(buffer), count, and offset:
length, count, offset = struct.unpack('!IIL', bytes)
And then waiting for `length' more bytes, which will be the buffer.
That was my intention, yes - I thought the header information of the OP
contained a byte count already.
I'm not sure what the original use-case was here. XML-RPC isn't a good
transport for arbitrary binary data. If `buffer' contains text, though,
that might be a good suggestion.
Certainly XMLRPC isn't too good - and Pyro in many aspects better. AFAIK it
uses pickle, and that means that things should be comparably compact.
Diez
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Re: help on packet format for tcp/ip programming
On 2007-02-08, [EMAIL PROTECTED] [EMAIL PROTECTED] wrote:
On Feb 8, 3:40 am, Grant Edwards [EMAIL PROTECTED] wrote:
On 2007-02-08, [EMAIL PROTECTED] [EMAIL PROTECTED] wrote:
struct module pack and unpack will only work for fixed size buffer :
pack('1024sIL', buffer, count. offset) but the buffer size can vary
from one packet to the next :-(
Oh for Pete's sake...
struct.pack('%dsIL' % len(buffer), buffer, count, offset)
that is great but how does one unpack on the other side?
struct.unpack('%dsIL' % buflen ,packet)
--
Grant Edwards grante Yow! Yow! Did something
at bad happen or am I in a
visi.comdrive-in movie??
--
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Re: help on packet format for tcp/ip programming
On 2007-02-08, Diez B. Roggisch [EMAIL PROTECTED] wrote:
struct module pack and unpack will only work for fixed size buffer :
pack('1024sIL', buffer, count. offset) but the buffer size can vary
from one packet to the next :-(
Oh for Pete's sake...
struct.pack('%dsIL' % len(buffer), buffer, count, offset)
that is great but how does one unpack on the other side?
By peeking into the header, determining the number of bytes necessary?
Better yet, use a protocol that's not brain-dead: send the
buffer size _before_ you send the buffer.
But why do you need this anyway - if you know that you will
have python on both ends, use Pyro or xmlrpc.
--
Grant Edwards grante Yow! A dwarf is passing
at out somewhere in Detroit!
visi.com
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Re: help on packet format for tcp/ip programming
[EMAIL PROTECTED] wrote: I want a specific packet format for packet exchange between a client server across the network. For example frame format as a python class could be: class Frame: def __init__(self, buffer=None, count=0, offset=0): self.buffer = buffer self.count = count self.offset = offset the question is how to convert it to a byte stream so that format of count and offset also becomes a sequence of bytes. Try struct. Regards, Björn -- BOFH excuse #208: Your mail is being routed through Germany ... and they're censoring us. -- http://mail.python.org/mailman/listinfo/python-list
Re: help on packet format for tcp/ip programming
On Feb 8, 1:43 am, Bjoern Schliessmann usenet-
[EMAIL PROTECTED] wrote:
[EMAIL PROTECTED] wrote:
I want a specific packet format for packet exchange between a
client server across the network. For example frame format
as a python class could be:
class Frame:
def __init__(self, buffer=None, count=0, offset=0):
self.buffer = buffer
self.count = count
self.offset = offset
the question is how to convert it to a byte stream so that format
of count and offset also becomes a sequence of bytes.
Try struct.
Regards,
Björn
--
BOFH excuse #208:
Your mail is being routed through Germany ... and they're censoring
us.
struct module pack and unpack will only work for fixed size buffer :
pack('1024sIL', buffer, count. offset) but the buffer size can vary
from one packet to the next :-(
-ishwar
--
http://mail.python.org/mailman/listinfo/python-list
Re: help on packet format for tcp/ip programming
On 7 Feb 2007 19:14:13 -0800, [EMAIL PROTECTED] [EMAIL PROTECTED]
struct module pack and unpack will only work for fixed size buffer :
pack('1024sIL', buffer, count. offset) but the buffer size can vary
from one packet to the next :-(
Then send the size of the buffer before the buffer, so the recipient
can expect that many bytes.
--
Felipe.
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Re: help on packet format for tcp/ip programming
En Thu, 08 Feb 2007 00:14:13 -0300, [EMAIL PROTECTED] escribió:
On Feb 8, 1:43 am, Bjoern Schliessmann usenet-
[EMAIL PROTECTED] wrote:
[EMAIL PROTECTED] wrote:
I want a specific packet format for packet exchange between a
client server across the network. For example frame format
as a python class could be:
class Frame:
def __init__(self, buffer=None, count=0, offset=0):
self.buffer = buffer
self.count = count
self.offset = offset
the question is how to convert it to a byte stream so that format
of count and offset also becomes a sequence of bytes.
Try struct.
struct module pack and unpack will only work for fixed size buffer :
pack('1024sIL', buffer, count. offset) but the buffer size can vary
from one packet to the next :-(
Use struct to pack count and offset into a fixed size field (2 or 4 bytes
depending on range); send buffer after that.
buffer must come *after* you send its size, else it's a lot harder to
retrieve at the other end.
--
Gabriel Genellina
--
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Re: help on packet format for tcp/ip programming
On 2007-02-08, [EMAIL PROTECTED] [EMAIL PROTECTED] wrote:
struct module pack and unpack will only work for fixed size buffer :
pack('1024sIL', buffer, count. offset) but the buffer size can vary
from one packet to the next :-(
Oh for Pete's sake...
struct.pack('%dsIL' % len(buffer), buffer, count, offset)
--
Grant Edwards grante Yow! I want the presidency
at so bad I can already taste
visi.comthe hors d'oeuvres.
--
http://mail.python.org/mailman/listinfo/python-list
